[unreadable] State-of-the-art rechargeable batteries are incapable of providing the high energy densities required in order to free the device-implanted patient from a tethered external power source. The ability to provide a left ventricular assisted device patient or totally artificial heart patient with significantly more time "off-tether" would greatly improve his or her quality of life. Therefore, the aim of our proposed research is to develop advanced electrolyte materials and formulations thereof that would safely enable the extraction of more energy from an implanted lithium-ion (Li-ion) rechargeable battery. In Phase I we formulated a new family of ionic liquid-based gel-polymer electrolytes with remarkable properties including non-flammability, enhanced oxidative stability, and resistance to thermal excursions under conditions of forced overcharge as determined by differential scanning calorimetry. Li-ion cells that incorporated the new electrolytes could be repeatedly cycled at physiological temperatures to high charge potentials resulting in a significant increase in energy density. In Phase II we propose to refine the gel-polymer electrolyte formulation, particularly in respect to Li-ion cell safety at high voltages. Under a Consortium Agreement with Wilson Greatbatch Technologies (WGT) (Clarence, NY), our advanced electrolytes will be incorporated into spiral wound AA cells. WGT will subject these cells to a variety of abuse conditions including forced overcharge at elevated temperatures. We anticipate that the successful completion of Phase II will lead to a broad spectrum of advanced Li-ion batteries that offer significantly higher energy densities than are achievable with conventional electrolytes. [unreadable] [unreadable]